1. Angiotensin II receptors on platelets were studied in 13 patients with uncomplicated type I diabetes mellitus and in 15 age-matched normal subjects.
2. Receptor density on cells from the diabetic patients was 15% lower than the normal subjects (5.2 ± 0.8 sd sites/platelet in diabetic patients and 6.4 ± 0.8 in normals, P < 0.001), but there were no differences in receptor affinity as measured by Kd (4.9 ± 1.5 × 10−10 mol/l in diabetic patients and 5.4 ± 1.4 × 10−10 mol/l in normals).
3. Plasma concentrations of renin and angiotensin II were similar in both groups.
4. The reduced density of angiotensin II receptors on platelets from patients with insulin-dependent diabetes may reflect a generalized abnormality of angiotensin II receptor regulation.